Excavation machines and similar, such as those used in public works and mining, are used to extract, move and load earth and rocks. These machines usually have a scoop joined to a mechanical arm. The scoop has a blade or a bevelled lip at the front edge, designed to impact and penetrate the mass of earth and rocks. In order to prevent excessive wear in the blade and to help to penetrate the earth, a number of teeth linked to the blade are usually mounted, which protrude from the front edge of the same. However, said teeth are also subjected to wear and breakage and should therefore be replaced frequently. Furthermore, depending on the work to be carried out by the machine, one may wish to change the type or shape of the teeth. In order to facilitate this replacement, a tooth holder is used, which is fastened to the blade of the scoop in a more or less permanent way, as well as a number of teeth, in such a way that each tooth is mounted freely in the tooth holder by means of a peg. Usually, this peg crosses a number of openings in the tooth and a passage that crosses the tooth holder, with the aim of fastening the tooth to the tooth holder, thus guaranteeing the connection between them.
When the sets of teeth and the tooth holder operate in difficult conditions, the peg that joins them together tends to move against the push force of a retention device or retainer element, which works with the peg to keep the tooth and the tooth holder together. Therefore, the peg may come out of the tooth holder and both the peg and the tooth could become lost. The loss of a tooth and/or peg may be very significant depending on the area in which work was being carried out with the same and may lead to other machines getting damaged, for example breakers, which work in the same production area as the machine using the teeth, for example in mines or quarries. As already indicated, a retention device linked to the peg is used to prevent the peg from coming out of its mounting position between the tooth and the tooth holder, which fastens the peg into said mounting position. The fastening devices, formed by at least one peg and at least one retainer element, usually have elastic characteristics, attributed to the fastening device by the retainer, so that the peg may be fastened and freed without it being necessary to break the same, this being a simple and preferably, hammer-less process, i.e. without it being necessary to use a hammer.
Retention devices or elements made of elastic material, such as rubber or polyurethane, are usually used, given that they have elastic characteristics which facilitate the creation of a system which is easy to dismount, without having to apply a high level of force. These retention elements are not useful for all kinds of work, owing to the fact that when they are used in applications in which the temperature of the material is high, the elastic material used may melt and/or lose its elastic qualities, therefore failing to retain the peg, which could also give rise to the peg and/or tooth getting lost.
U.S. Pat. No. 5,233,770 describes a peg system formed by an elongated body with a proximal end and a distal end. The proximal end serves as an impact surface, whilst the distal end serves to guide the introduction of the peg into the coupling or mounting formed by the two components. Likewise, this peg has a stopper element, which extends towards the outside of the main body, this limiting the course for inserting the peg, so that the same does not exceed its mounting position. Furthermore, the peg has a built-in spring at a certain angle, which may be compressed when inserting the peg but which recovers its usual position in the mounting position. This peg system is very rigid and the force needed to introduce and above all, extract this kind of peg is very high, i.e. a mallet or hammer is needed to extract the peg and to make it possible to uncouple the male and female components, given that it is necessary to apply considerable force in order to break the stopper element.
The fastening system described in U.S. document number U.S. Pat. No. 5,724,756 has a spring system for fastening the rear cavity of a hunt tooth to the mounting flange of an adaptor. Said fastening system is not very reliable or stable, given that both whilst introducing the same as well as when the same is in operation, it tends to move in an uncontrolled manner, which could jam the system mid extraction as well as lead to the loss of the elastic properties, which are claimed to create tension in the system, thus giving rise to the loss of this function. Furthermore, this retention system requires an additional retention system so that the peg body does not move from its mounting position.